1. Field of the Invention
This invention relates to a process for upgrading hydrocarbonaceous fluids and, particularly, to a process for upgrading retorted shale oil prior to dearsenation by contacting the oil at moderate temperatures over a catalytic guardbed in the presence of hydrogen. The catalytic guardbed comprises deactivated guard chamber or hydrotreating catalyst from a downstream operation.
2. Description of Prior Art
Due to the scarcity of other hydrocarbon fuels and energy resources in general, shale oil and other hydrocarbonaceous fluids such as those derived from coal, bituminous sands, etc., are expected to play an increasing role in the production of commercial hydrocarbon fuels in the near future. Substantial effort is being devoted to the development of cost-efficient refining techniques for the processing of these hydrocarbonaceous fluids. For the purposes of this invention, hydrocarbonaceous fluids include crude oil, heavy oil, vacuum residue, solvent-deasphalted oil, solvent-deasphalted residue, crack oil, shale oil, tar sand oil and natural asphalt. These hydrocarbons contain various non-metallic and metallic impurities which may adversely affect further hydrocarbon treatment processes. Of the trace metals in the hydrocarbonaceous fluids, arsenic and iron are the most predominant, e.g., greater than 20 ppm. Failure to remove these metals during the upgrading process often results in processing problems. For example, some arsenic compounds are water soluble and thus can cause pipeline corrosion. Additionally, when hydrocarbons are upgraded by delayed coking, many of the metals are rejected in the coke, resulting in lower quality coke. Further, the upgraded catalysts are irreversibly poisoned by the metals deposition. Further, many hydrocarbons have potential As.sub.2 O.sub.3 emission problems when burned directly as a fuel. As a result, it is preferable to remove these metals from the hydrocarbonaceous fluids prior to any downstream processing, or direct use.
Removing these metals generally requires reaction temperatures of 500.degree. F. or greater. These reaction temperatures result in polymerization or coking reactions by the conjugated diolefins present in the hydrocarbonaceous fluids, which cause fouling problems in the reaction. Therefore, both trace metals and conjugated diolefins must be removed from the hydrocarbonaceous fluids in order to reduce excessive polymerization or coking during the downstream operations.
Saturation of the olefins can take place in the presence of hydrogen. It is commonly known in the petroleum industry to use palladium or platinum as pyrolysis gasoline saturation catalysts for this process. These catalysts, while retaining diolefin saturation activity, have virtually no aromatic saturation activity.
Nickel arsenide has been shown in prior art to be an effective catalyst for selective hydrogenation of diolefins to monoolefins. Johnson (U.S. Pat. Nos. 3,697,448; 3,787,511; U.S. Pat. No. 3,900,526 and U.S. Pat. No. 4,020,119) is directed to the use of nickel arsenide aluminum catalysts for the selective hydrogenation of diolefins. These compounds can also hydrogenate organic sulfur compounds, carbonyls and acetylenes. Additionally, antimony can be used in place of arsenic and nickel can be substituted with iron and/or cobalt. The reaction is carried out at temperatures of 75.degree.-750.degree. F., a pressure of 1000 psig and a LHSV (liquid hourly space velocity) of 0.1 to 10.
The use of nickel-containing catalysts for dearsenation is also known. Wunderlich (U.S. Pat. No. 4,069,140) is directed to the use of NiS and MoS.sub.3 on Al.sub.2 O.sub.3 as well as high pore volume supported nickel. Young (U.S. Pat. No. 4,046,674) is directed to the use of a NiMo/refractory oxide catalyst.
The use of NiMo/Al.sub.2 O.sub.3 for hydrodenitrogenation of shale oil is well known in the literature. See for example J. R. Katzer and R. Sivasubramarian, Catal. Rev. Sci. Eng. 20(2), 155-208, (1979). The catalysts described therein are irreversibly poisoned by arsenic and consequently must be discarded because 100% dearsenaton of shale oil in the guard chamber is probably not feasible.
While all of these processes may be effective, they generally employ relatively expensive catalysts which are permanently deactivated and thus discarded. Additionally, many of the reactions described in the foregoing processes require reaction temperatures which would induce olefinic polymerization and thus reactor fouling.